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Fabrication of Multi-Functional Sintered Materials with Graded Compositional Distribution

具有梯度成分分布的多功能烧结材料的制造

基本信息

批准号：
03453064
负责人：
WATANABE Ryuzo
金额：
$ 4.42万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1993
项目状态：
已结题

项目摘要

A laser beam differential temperature heating test and a hydrogen/oxygen burner flame heating test were made on the graded specimens of metal and ceramics, fabricated under the design scheme established in the forgoing two years. An acoustic emission monitoring was used to detect the crack formation in the specimen during heating and cooling cycle. Vertical cracks were observed to be formed during cooling cycle of testings. The vertical cracks propagated by further heating and cooling, and they eventually coalesce to result in the spallation of the ceramic layr from specimen surface. Finite element analysis on the stress state in the specimen was done using the measured temperature distribution, and it has shown that a large compressive stress is generated during heating period at the ceramic surface to cause non-elastic deformation of the ceramic layr. The non-elastic deformation will cause during cooling peiod tensile stress, which will exceed the intrinsic strength of the ceramics and result in the formation of the vertical cracks. From the microstructural observations of the crack propagation in the composite structures consisted of metal and ceramic phase the improvement of the ductility of the ceramic-rich regions has been found to be indispensible for the retention of the heat resisrtance of this kind of functionally gradient materials. Such an improvement will be realized by an control of the connectivity of the metal phase in the ceramic-rich region through a process optimization. The heat insulating performance is evaluated by thermal resistance of the material, and its value is a characteristic parameter, along with the heating temperature of the vertical crack formation, for the thermomechanical performance of functionally gradient materials. The concept of the microstructual control of graded materials, particulary with respect to the connectivity of the phases involved, will be applied to the other kind of functionally gradient materials, such as ther

对根据前两年制定的设计方案制作的金属和陶瓷分级试件进行了激光束差温加热试验和氢/氧燃烧器火焰加热试验。声发射监测用于检测加热和冷却循环过程中样品中裂纹的形成。在测试的冷却循环期间观察到形成垂直裂纹。垂直裂纹通过进一步加热和冷却而扩展，最终合并导致陶瓷层从样品表面剥落。利用测得的温度分布对试件内的应力状态进行有限元分析，结果表明，在加热过程中陶瓷表面产生较大的压应力，导致陶瓷层发生非弹性变形。非弹性变形在冷却过程中会产生拉应力，超过陶瓷的固有强度，导致垂直裂纹的形成。从金属和陶瓷相复合结构中裂纹扩展的微观结构观察发现，富陶瓷区域延展性的提高对于保持这种功能梯度材料的耐热性是必不可少的。这种改进将通过工艺优化控制富陶瓷区域金属相的连通性来实现。隔热性能是通过材料的热阻来评价的，其值与垂直裂纹形成的加热温度一起是功能梯度材料热机械性能的特征参数。梯度材料的微观结构控制的概念，特别是涉及相的连接性，将应用于其他类型的功能梯度材料，例如热梯度材料。